Sensitivity of Headland Bypassing to Variations in Local Wave Conditions
and Regional Climate Drivers
Abstract
Headland sediment transport is dynamic and complex, but understanding
the transport mechanisms is necessary for effective long-term management
of downdrift beach compartments. In this study, we have develop a
coastal process model using TUFLOWFV, that is used to calibrate an
approximation tool for headland bypassing at the study site. The
approximation tool is shown to reproduce sediment transport rates at the
headland apexes accurately and efficiently. We have explored the
headland sediment transport mechanism, the influence of wave height and
direction, and the sensitivity in regional climate conditions. Headland
sediment transport is shown to occur as ‘trickle’ bypassing under modal
wave conditions or ‘sand slug’ migration under storm wave conditions
that travel in either a headland-attached and a cross-embayment pathway.
Bypassing during storm wave conditions produces 50% to 60% of total
bypassing volume, despite only accounting for 6% of the recorded days.
The results indicate that headland transport is sensitive to changes in
wave direction and wave height, with the existing mean wave direction
balancing sediment transport on the east and north faces of the
headland. Seasonality is the most significant climatic control on
headland transport, while ENSO phase is only significant for the
headland apexes that are exposed to south-east wave conditions. The
potential for anticlockwise rotation of the wave climate in future is
explored, with greater erosion of the northern beaches of the headland
likely due to a reduced supply of sediment around the eastern point of
the headland and greater erosive wave power on the north side.